The murmur in this heart sound may be difficult to be appreciated, but what is heard is an S3 gallop sound.
The third and fourth heart sounds occur during diastole and are not normally audible in normal dogs. The S3 heart sound is lower in frequency than S1 and S2 sounds, and it is usually best heard with the bell of the stethoscope. An S3 may sound like horse galloping, hence the term gallop heart sounds; however, the term gallop rhythm should be avoided, as an audible S3 does not relate to the heart’s underlying electrical rhythm. Rapid ventricular filling generates the S3 (also known as S3, protodiastolic, or ventricular gallop). An audible S3 is most commonly heard with diastolic volume overloading, as seen in this patient with severe mitral insufficiency.